Maybe there is a mixture of bacteria,viruses and unicellular evolution.
Human beings maybe is not begin as 2 person as Adam and Eve.Let's say for example:When the above combination of micro organisms travel to one of the area or country.It affect these creatures together maybe is those Apes or some other creatures.These organisms will change them to human being together.
And because these human being cells can travels by air,they will travel to other area or country to form new human beings maybe at different times or at the same time.Due to different environment and the food they eat.They will have different gene.That why there are different plants,animals etc.But belong to the same group.
For cat,there are different types of cats with different gene.Yet they live in different countries and are so far.Do u think they can travel so far to reproduce.I guess not.The only way is to travel by air with their "cat" cells to these countries.
It's the same to plants etc.When the evolution of one type of cell is formed,it's spread like viruses through air to create new species.
Why human being are able to communicate is because when they meet, and share with maybe by hands signals and drawing as those cave man did.And soon they are able to create words to make communication easiers.
So to my conclusion human maybe is formed not just 2 person but with many and with different species.At different times or same due to the air travel of human being genes cells to different creatures at different countries.